Extraordinary Hall effect in nanoscale nickel films

The extraordinary Hall effect was studied in 1 to 10nm thick nickel films prepared by radio-frequency diode sputtering (plasma) and electron-beam evaporation of Ni. The Hall resistance, RH, does not reach saturation in fields up to 0.5 T in films that are not uniform while for uniform films, RH saturates at 0.3 T. The films prepared by plasma sputtering showed a jump-like behavior of the extraordinary Hall coefficient, RS, that is due to the presence of two phases—tetragonal (nonmagnetic) and face-centered cubic(fcc) (magnetic)—in the initial growth stage and subsequent phase transition of the tetragonal lattice to fcc at a film thickness of about 4 nm around which the extraordinary Hall coefficient RS increases abruptly reaching its maximum. The films prepared by electron-beam evaporation consist only of the fcc phase and have a dome-like RS dependence on film thickness.